Indicator lamps, such as incandescent switchboard lamps, are used in telecommunication systems in great numbers. The cost of the lamps in relationship to their lifetime is a critical factor in the economical operation of such systems.
Efficient testing and sorting methods applied to mass produced articles can significantly lower the cost of such articles. In the recent past, solid state replacements for switchboard lamps have been developed. (See U.S. Pat. No. 4,054,814, assigned to the assignee of records.) These replacements desirably retain the characteristics of luminescence and hue of the switchboard lamps, but in addition they exhibit a longer lifetime than their incandescent counterparts. A higher cost of these replacements can, of course, offset the advantage of an increased lifetime over the conventional lamps. It is, therefore, desirable to minimize manual steps in the production of the replacements.
The prior art includes a testing and sorting process in which an operator loads the replacement devices or articles into a test socket. Before the articles are loaded into the socket, they are manually oriented in a certain direction which aligns electrical contacts of the articles always in the same direction with a test circuit. A test is then performed which indicates, among possible other feedbacks, whether the tested article exhibits the correct hue and brightness in response to an applied test voltage. Individual handling of each article in preparation for this test and a subsequent manual sorting operation is cumbersome and adds significantly to the cost of the articles.
Automatic testing is well known in various phases of production of solid state electronic articles. However, with respect to some electronic articles manual handling is necessary. Because of the peculiar size and shape of some articles, automatic handling has not become available for them.
In the past, light emitting diodes (LEDs) have already been handled automatically in a brightness and hue test. An apparatus for testing LEDs has, for example, been disclosed in B. C. Abraham et al., "Light Emitting Diode Test Apparatus," No. 39 technical digest (Western Electric, pub., July, 1975). The prior art apparatus shows a vibratory feeder bowl which is well known for handling small electronic articles. Articles fed from the bowl enter a vibratory track and are received, one by one, in one of a number of slots spaced around a rotary table. As the table is indexed fron position to position, a new article is loaded at each step, an already loaded article is tested and one or more tested articles are discharged into bins located at consecutive stations about the periphery of the table. The decision to discharge a certain one of the articles into one or another of the bins is based on the test. "Smart" test circuits to make such decisions are well known in the art.
In the diode test apparatus of the prior art, a problem of alignment of the article in the receiving slot of the table did not occur. The diodes to be tested had a two-leaded configuration similar to that of other electronic articles. And it is possible to apply a test voltage first in one direction, and then in the other. If a light output from the diode in either one of the two directions meets desired specification, the two-leaded device is acceptable.
However, the articles to be tested in accordance with the present invention are already marked as to their polarity. A mere indication of a functional article tested in one of two directions is insufficient to test for the acceptability of such an article.
Also the articles to be tested have a molded shape which does not correspond to the usual shapes of solid state articles. It is consequently desirable to orient articles such as solid state lamp replacements to align their contacts with contacts in a test apparatus.
It is further required to ascertain whether the light emitting chips within the articles are correctly oriented. Each article may only light up when a voltage is applied to the terminals of the article in a predetermined direction with respect to an external polarity marking on the article.